The present invention relates to an industrial robot hand. More particularly, the present invention relates to a mechanical hand which can be connected to an industrial robot, for example to the end wrist portion of the arm of an industrial robot, to handle material.
Various kinds of material handling apparatus, such as robots, manipulators, fork lift trucks, cranes, and the like, have been put into practical use. Such apparatus frequently includes a mechanical hand for grasping material. These hands can mainly be classified into mechanical hands of the finger type, having claw-like engaging members to hold material, and mechanical hands of the fingerless type, having no engaging member.
Finger type mechanical hands can be classified into hands which hang down, hands which pinch, hands which sandwich, and hands which grasp, among others. In particular, in the case of sandwiching type mechanical hands, the engaging members are inserted from both sides of the material to be grasped, into or under the bottom portion thereof or into the lateral holes formed in the material, thereby permitting lifting up or moving the material. It is necessary to accurately locate the mechanical hand to a proper grasping position, e.g. just above the material. If the hand is not accurately positioned, the engaging members will not be properly located on both sides of the material, and so the material cannot be properly grasped.
It is possible to accurately position the mechanical hand of an industrial robot. However, there is a possibility that the position of the material to be grasped has deviated from the expected position. It is difficult always to accurately set the material at a constant position. Thus, an improved technique is needed to position the hand of an industrial robot accurately with respect to the material. In the work of stacking material, when an industrial robot piles up materials at a fixed coordinate position, it may be unclear whether the material has in fact been stacked at the position designated by the robot hand as the coordinate position. In practice, in many cases the position of the material slightly deviates from the coordinate position. Particularly, when the material has engaging portions, it cannot be properly stacked if the positions of different pieces of material in the stack deviate from the coordinate position.
On the other hand, when material is packaged within soft packaging, or when the dimensional accuracies of the containers in which the material is enclosed are low, or when pallet on which material is mounted is deformed, or the like, stacked materials may not be aligned properly in the vertical direction. Therefore, the engaging members of the mechanical hand cannot be lowered properly because the engaging members touch the material the position of which deviates relative to the position of other material.
As a solution for such a problem, it is possible to utilize apparatus providing a video input that is recognized or to utilize a method or an apparatus including a sensor, whereby the position is corrected and controlled by the sensor output. However, these methods have the drawback of an increase in cost.